Just figured I'd post this quick update. My water was beginning to turn tea colored again, even with the carbon in the filter. I decided to throw in a bag of Purigen to see what would happen, and I have to say, I'm pretty impressed!
This is the tank yesterday, before Purigen:
This is the tank this afternoon, not even 24 hours later:
I used the exact same camera settings (white balance, EV Shift, etc.) to take both pictures. Pretty noticeable difference.